import sys, os, math, bisect, itertools, collections, heapq, queue, copy, array

# from scipy.sparse.csgraph import csgraph_from_dense, floyd_warshall
# from decimal import Decimal
# from collections import defaultdict, deque

sys.setrecursionlimit(10000000)

ii = lambda: int(sys.stdin.buffer.readline().rstrip())
il = lambda: list(map(int, sys.stdin.buffer.readline().split()))
fl = lambda: list(map(float, sys.stdin.buffer.readline().split()))
iln = lambda n: [int(sys.stdin.buffer.readline().rstrip()) for _ in range(n)]

iss = lambda: sys.stdin.buffer.readline().decode().rstrip()
sl = lambda: list(map(str, sys.stdin.buffer.readline().decode().split()))
isn = lambda n: [sys.stdin.buffer.readline().decode().rstrip() for _ in range(n)]

lcm = lambda x, y: (x * y) // math.gcd(x, y)

MOD = 10 ** 9 + 7
INF = float('inf')


def main():
    if os.getenv("LOCAL"):
        sys.stdin = open("input.txt", "r")

    K = ii()

    ret = []
    for i in range(K + 1):
        if i == 0:
            ret.append(7 % K)
        else:
            ret.append((ret[i - 1] * 10 + 7) % K)
    for i in range(K + 1):
        if ret[i] == 0:
            print(i + 1)
            exit()
    else:
        print(-1)


if __name__ == '__main__':
    main() import sys, os, math, bisect, itertools, collections, heapq, queue, copy, array sys os math bisect itertools collections heapq queue copy array sys.setrecursionlimit(10000000) sys.setrecursionlimit sys setrecursionlimit 10000000 ii = lambda: int(sys.stdin.buffer.readline().rstrip()) ii lambda: int(sys.stdin.buffer.readline().rstrip()) int(sys.stdin.buffer.readline().rstrip()) int sys.stdin.buffer.readline().rstrip() sys.stdin.buffer.readline().rstrip sys.stdin.buffer.readline() sys.stdin.buffer.readline sys.stdin.buffer sys.stdin sys stdin buffer readline rstrip il = lambda: list(map(int, sys.stdin.buffer.readline().split())) il lambda: list(map(int, sys.stdin.buffer.readline().split())) list(map(int, sys.stdin.buffer.readline().split())) list map(int, sys.stdin.buffer.readline().split()) map int sys.stdin.buffer.readline().split() sys.stdin.buffer.readline().split sys.stdin.buffer.readline() sys.stdin.buffer.readline sys.stdin.buffer sys.stdin sys stdin buffer readline split fl = lambda: list(map(float, sys.stdin.buffer.readline().split())) fl lambda: list(map(float, sys.stdin.buffer.readline().split())) list(map(float, sys.stdin.buffer.readline().split())) list map(float, sys.stdin.buffer.readline().split()) map float sys.stdin.buffer.readline().split() sys.stdin.buffer.readline().split sys.stdin.buffer.readline() sys.stdin.buffer.readline sys.stdin.buffer sys.stdin sys stdin buffer readline split int(sys.stdin.buffer.readline().rstrip()) for _ in range(n) for _ in range(n) _ range(n) range n for _ in range(n) int(sys.stdin.buffer.readline().rstrip()) int sys.stdin.buffer.readline().rstrip() sys.stdin.buffer.readline().rstrip sys.stdin.buffer.readline() sys.stdin.buffer.readline sys.stdin.buffer sys.stdin sys stdin buffer readline rstrip iln = lambda n: [int(sys.stdin.buffer.readline().rstrip()) for _ in range(n)] iln lambda n: [int(sys.stdin.buffer.readline().rstrip()) for _ in range(n)] [int(sys.stdin.buffer.readline().rstrip()) for _ in range(n)] n iss = lambda: sys.stdin.buffer.readline().decode().rstrip() iss lambda: sys.stdin.buffer.readline().decode().rstrip() sys.stdin.buffer.readline().decode().rstrip() sys.stdin.buffer.readline().decode().rstrip sys.stdin.buffer.readline().decode() sys.stdin.buffer.readline().decode sys.stdin.buffer.readline() sys.stdin.buffer.readline sys.stdin.buffer sys.stdin sys stdin buffer readline decode rstrip sl = lambda: list(map(str, sys.stdin.buffer.readline().decode().split())) sl lambda: list(map(str, sys.stdin.buffer.readline().decode().split())) list(map(str, sys.stdin.buffer.readline().decode().split())) list map(str, sys.stdin.buffer.readline().decode().split()) map str sys.stdin.buffer.readline().decode().split() sys.stdin.buffer.readline().decode().split sys.stdin.buffer.readline().decode() sys.stdin.buffer.readline().decode sys.stdin.buffer.readline() sys.stdin.buffer.readline sys.stdin.buffer sys.stdin sys stdin buffer readline decode split sys.stdin.buffer.readline().decode().rstrip() for _ in range(n) for _ in range(n) _ range(n) range n for _ in range(n) sys.stdin.buffer.readline().decode().rstrip() sys.stdin.buffer.readline().decode().rstrip sys.stdin.buffer.readline().decode() sys.stdin.buffer.readline().decode sys.stdin.buffer.readline() sys.stdin.buffer.readline sys.stdin.buffer sys.stdin sys stdin buffer readline decode rstrip isn = lambda n: [sys.stdin.buffer.readline().decode().rstrip() for _ in range(n)] isn lambda n: [sys.stdin.buffer.readline().decode().rstrip() for _ in range(n)] [sys.stdin.buffer.readline().decode().rstrip() for _ in range(n)] n lcm = lambda x, y: (x * y) // math.gcd(x, y) lcm lambda x, y: (x * y) // math.gcd(x, y) (x * y) // math.gcd(x, y) x * y x y math.gcd(x, y) math.gcd math gcd x y x y MOD = 10 ** 9 + 7 MOD 10 ** 9 + 7 10 ** 9 10 9 7 INF = float('inf') INF float('inf') float 'inf' def main():
    if os.getenv("LOCAL"):
        sys.stdin = open("input.txt", "r")

    K = ii()

    ret = []
    for i in range(K + 1):
        if i == 0:
            ret.append(7 % K)
        else:
            ret.append((ret[i - 1] * 10 + 7) % K)
    for i in range(K + 1):
        if ret[i] == 0:
            print(i + 1)
            exit()
    else:
        print(-1) main if os.getenv("LOCAL"):
        sys.stdin = open("input.txt", "r")

     os.getenv("LOCAL") os.getenv os getenv "LOCAL" sys.stdin = open("input.txt", "r") sys.stdin sys stdin open("input.txt", "r") open "input.txt" "r" K = ii() K ii() ii ret = [] ret [] for i in range(K + 1):
        if i == 0:
            ret.append(7 % K)
        else:
            ret.append((ret[i - 1] * 10 + 7) % K)
     i range(K + 1) range K + 1 K 1 if i == 0:
            ret.append(7 % K)
        else:
            ret.append((ret[i - 1] * 10 + 7) % K)
     i == 0 i 0 ret.append(7 % K) ret.append ret append 7 % K 7 K ret.append((ret[i - 1] * 10 + 7) % K) ret.append ret append (ret[i - 1] * 10 + 7) % K ret[i - 1] * 10 + 7 ret[i - 1] * 10 ret[i - 1] ret i - 1 i 1 10 7 K for i in range(K + 1):
        if ret[i] == 0:
            print(i + 1)
            exit()
    else:
        print(-1) i range(K + 1) range K + 1 K 1 if ret[i] == 0:
            print(i + 1)
            exit()
     ret[i] == 0 ret[i] ret i 0 print(i + 1) print i + 1 i 1 exit() exit print(-1) print -1 if __name__ == '__main__':
    main() __name__ == '__main__' __name__ '__main__' main() main lcm = lambda x, y: (x * y) // math.gcd(x, y) lambda x, y: (x * y) // math.gcd(x, y) lcm def main():
    if os.getenv("LOCAL"):
        sys.stdin = open("input.txt", "r")

    K = ii()

    ret = []
    for i in range(K + 1):
        if i == 0:
            ret.append(7 % K)
        else:
            ret.append((ret[i - 1] * 10 + 7) % K)
    for i in range(K + 1):
        if ret[i] == 0:
            print(i + 1)
            exit()
    else:
        print(-1) def main():
    if os.getenv("LOCAL"):
        sys.stdin = open("input.txt", "r")

    K = ii()

    ret = []
    for i in range(K + 1):
        if i == 0:
            ret.append(7 % K)
        else:
            ret.append((ret[i - 1] * 10 + 7) % K)
    for i in range(K + 1):
        if ret[i] == 0:
            print(i + 1)
            exit()
    else:
        print(-1) main il = lambda: list(map(int, sys.stdin.buffer.readline().split())) lambda: list(map(int, sys.stdin.buffer.readline().split())) il INF = float('inf') float('inf') INF iss = lambda: sys.stdin.buffer.readline().decode().rstrip() lambda: sys.stdin.buffer.readline().decode().rstrip() iss isn = lambda n: [sys.stdin.buffer.readline().decode().rstrip() for _ in range(n)] lambda n: [sys.stdin.buffer.readline().decode().rstrip() for _ in range(n)] isn MOD = 10 ** 9 + 7 10 ** 9 + 7 MOD fl = lambda: list(map(float, sys.stdin.buffer.readline().split())) lambda: list(map(float, sys.stdin.buffer.readline().split())) fl ii = lambda: int(sys.stdin.buffer.readline().rstrip()) lambda: int(sys.stdin.buffer.readline().rstrip()) ii iln = lambda n: [int(sys.stdin.buffer.readline().rstrip()) for _ in range(n)] lambda n: [int(sys.stdin.buffer.readline().rstrip()) for _ in range(n)] iln sl = lambda: list(map(str, sys.stdin.buffer.readline().decode().split())) lambda: list(map(str, sys.stdin.buffer.readline().decode().split())) sl
import sys, os, math, bisect, itertools, collections, heapq, queue, copy, array

# from scipy.sparse.csgraph import csgraph_from_dense, floyd_warshall
# from decimal import Decimal
# from collections import defaultdict, deque

sys.setrecursionlimit(10000000)

ii = lambda: int(sys.stdin.buffer.readline().rstrip())
il = lambda: list(map(int, sys.stdin.buffer.readline().split()))
fl = lambda: list(map(float, sys.stdin.buffer.readline().split()))
iln = lambda n: [int(sys.stdin.buffer.readline().rstrip()) for _ in range(n)]

iss = lambda: sys.stdin.buffer.readline().decode().rstrip()
sl = lambda: list(map(str, sys.stdin.buffer.readline().decode().split()))
isn = lambda n: [sys.stdin.buffer.readline().decode().rstrip() for _ in range(n)]

lcm = lambda x, y: (x * y) // math.gcd(x, y)

MOD = 10 ** 9 + 7
INF = float('inf')


def main():
    if os.getenv("LOCAL"):
        sys.stdin = open("input.txt", "r")

    K = ii()

    ret = []
    for i in range(K + 1):
        if i == 0:
            ret.append(7 % K)
        else:
            ret.append((ret[i - 1] * 10 + 7) % K)
    for i in range(K + 1):
        if ret[i] == 0:
            print(i + 1)
            exit()
    else:
        print(-1)


if __name__ == '__main__':
    main()
